Study on Air-Purifying Performance of Semi-Flexible Asphalt Samples Coated with Titanium Dioxide Using Different Methods

Titanium dioxide (TiO2) was recently employed to apply onto road surfaces to degrade the harmful compounds from vehicle emissions. However, it remains a challenging task to find a highly compatible pavement type for TiO2 application to achieve durable and efficient air-purifying performance. This study proposed to coat TiO2 particles onto semi-flexible pavement surface and tried to investigate an optimum coating method. Three coating methods, including direct mixing TiO2 (MT) with asphalt mixture, spraying dry TiO2 (ST) coating and watersolution- based TiO2 (WT) coating on semi-flexible pavement surface. To achieve this objective, semi-flexible samples were prepared to evaluate and compare the performances of three coating methods by employing resistance to wearing, NO removal efficiency tests and residual texture depth tests. It was found that the ST method not only provided better NO degrading efficiency but also improved the resistance to wearing than the other two methods.